1. Field of the Invention
The present invention relates to apparatuses for silencing electromagnetic noise, and more specifically, to an apparatus for silencing electromagnetic noise and configured for use with integrated circuits and printed circuit boards.
2. Description of Related Art
High frequency digital circuit design is moving toward the trend of high speed, small volume, and low voltage. As such, the effect of the ground bounce noise (GBN) in the integrated circuit on the circuit system is also becoming more and more obvious.
Ground bounce noise is a transient voltage generated between a power plane and a ground plane during high speed switching of integrated circuit in a high-speed digital circuit, thereby forming parasitic noise at the connection of the signal line and the power plane. In addition, as the switching speed of the system gets faster, and the number of IC pins with simultaneous logic state conversion increases, the phenomenon of the ground bounce noise will become more significant.
In the conventional ground bounce noise suppression technique, the most frequently used method is to increase the number of decoupling capacitors around the noise source so as to offset the fluctuation of the voltage wave traveling through the plane. If a plurality of capacitors are peripherally provided on the IC susceptible to the interference, a capacitor wall can then be formed to contain the signal energy inside the wall.
However, as the high frequency circuit layout gets more complex on a very large-scale integrated circuit, adding a capacitor wall to a complex circuit design will significantly increase the complexity of the circuit layout. In addition, capacitor is a passive component of a relatively large size, thus if a plurality of capacitive components are used to form the enclosed capacitor wall, cost and space of the integrated circuit will definitely be increased.
Another conventional method to suppress ground bounce noise is to cut a rectangular crevice on the power plane or the ground plane, thereby containing the noise inside the crevice so as to avoid the internal noise to interfere with the function of other external components.
However, there are disadvantages of cutting crevices on the power plane to suppress the ground bounce noise effect, namely reduction of the power plane area, and interruption of the DC power offset inside and outside the crevices. As the internal signal line is coupled to the external components, crevices must be crossed, thereby generating more serious signal quality and electromagnetic radiation problems.
In order to avoid the signal quality and electromagnetic radiation problems generated as the connection of the internal signal line and the external components crosses crevices, a small through route is technically reserved at the surroundings of the crevices, thereby maintaining the consistency of the internal and external offsets. However, this would allow the inrush current to traverse the external part to lower the suppressing effect of the crevices cut.
Finally, referring to FIG. 1, a diagram of conventional technique is shown. As shown in the diagram, cylinders of a high dielectric constant are placed between a power plane and a ground plane at a regular interval, thereby forming an omnidirectional noise suppression frequency band. However, the cost of manufacturing such cylinders of a high dielectric constant is very high and a special process is required. Hence the manufacturing cost of this technique is usually higher than any other techniques.
In summary, it has become an urgent issue to designers of the field to develop a key technology to provide an apparatus that suppresses ground bounce noise to avoid the drawback such as significant increase in the cost and space of the integrated circuit due to the use of an enclosed capacitor wall, and eliminates the signal quality and electromagnetic radiation problems generated as the connection of the internal signal line and the external components crosses crevices. In addition, the apparatus shall also lower the high cost required in manufacturing cylinders of a high dielectric constant.